THE LEAF 



85 



a > mo ^ e ^ attachment of the tendril 

 tips to a support; 6, the clawed ex- 

 tremity, enlarged. 



Lathyrus Aphaca (Fig. 72) only the stipules remain to 

 perform the offices of the blade. 



148. One of the most 

 remarkable of tendril 

 leaves is that of the 

 Cobcea figured herewith 

 (Fig. 73). The tendril 

 portion branches several 

 times. Each branch 

 again divides and sub- 

 divides. The final sub- 

 divisions are clawed 

 (Fig. 74). 



Owing to the dichot- 



omous or two-forked branching, neighboring claws 

 cooperate in catching slender objects coming into the axils 



of the dichotomy, as the 

 jaws of a pair of ice tongs 

 act together in holding the 

 block of ice. The tendril, 

 therefore, catches with great 

 readiness upon anything it 

 may strike as the leaf is 

 swayed by the breeze. Yet 

 the leaf is far from depend- 

 ent upon the winds for mo- 

 tion. Like the extremity 

 of a twining stem, it makes 

 regular revolutions. The 

 leaf from which the figure 

 was drawn made complete 

 revolutions in one hour and 

 ten minutes, the end swing- 

 ing round a circle about one 

 foot in diameter. The mo- 

 tion is easy to see, since the 

 average rate of progress is about one-third the rate at 

 which the end of the second hand of a watch travels. 



75. Coiling of the tendril after having 

 fastened to a support. 



